Nissan Motor Company Limited

Mikio Ura

Takeshi Miyamoto

Mikio Kawai

Shigenori Kazama

Harutoshi Miyagi

Takao Kase

Yoshiko Maeda

The invention relates to a variable light transmittance glass board which is an electrochromic cell in principle and is comprised of oppositely arranged two transparent glass substrates each of which is laid with a transparent electrode film, first and second electrochromic layers formed on the two electrode films, respectively, by using tungsten trioxide for the first layer and Prussian blue for the second layer and an electrolyte liquid which fills up the space remaining between the two electrode films. The electrolyte liquid is a solution of a conventional supporting electrolyte such as lithium perchlorate in an organic polar solvent such as propylene carbonate. Durability of both electrochromic layers at elevated temperatures is greatly improved by adding 0.2-3.0 wt % of water to the organic polar solvent. By using one or two auxiliary electrode(s) comprising an electrochemically oxidizable and reducible material and being disposed in a marginal region of the space between the two glass substrates, it is possible to prevent the appearance of the glass board from being marred by partial decomposition of the electrolyte liquid at the initial reduction of one electrochromic layer. A polymer of a conjugated compound, e.g. polytriphenylamine, is very advantageous as the electrochemically active material in each auxiliary electrode.

Variable light transmittance glass board functional as electrochromic

An electrochromic device having two electrochromic layers respectively formed on oppositely arranged two electrodes and containing an electrolyte such as a solution of an alkali metal salt in an organic solvent which fills up the gap between the two electrodes. The electrochromic layers are formed of an electrochromic material which can alternately and stably exist in three different oxidation states and assumes three different colors in its respective oxidation states such that there is a clear contrast between the color of this material in its normal or intermediate oxidation state and a composite color given by superposition of the color in the highest oxidation state on the color in the lowest oxidation state. Prussian blue is a preferred example of such an electrochromic material, on condition that an adequate amount of water be present in the electrolyte solution or, alternatively, that the Prussian blue layers be pretreated to substitute alkali metal cation for Fe.sup.3+ interstitially existing in the crystal lattice of Prussian blue.

Electrochromic device

Growing community of inventors

Yokohama, Japan

Mikio Ura